Biological materials such as enzymes or enzyme-producing microorganisms or cells, are often used as catalysts for synthetic reactions and for analytical techniques. Such catalysts are desirable because they operate with high specificity and efficiency under generally mild reaction conditions.
Because enzymes and other biocatalysts are generally water-soluble, they are suited for use in batch-type reaction systems. Reuse of such enzymes and other biocatalysts is limited because of difficulties in recovering those materials from the spent reaction medium in active or usable form. Moreover, the materials tend to remain in the prepared product as contaminants. In order to avoid these problems, methods have been developed to immobilize biological materials which exhibit catalytic activity on insoluble solid supports. Immobilization is intended to result in a stabilized biological material which can withstand the rigors of repeated or continuous use.
Several immobilization systems for biological materials have been reported. Enzymes have been immobilized by absorption onto insoluble materials such as charcoal, glass, cellulose, calcium phosphate gel, montmorillonite and organic ion-exchange resins among others. Immobilization has also been achieved by entrapment within starch and acrylamide gels, covalent attachment between enzymes and insoluble organic polymers, as well as covalent attachment between enzyme molecules themselves.
The processes of the prior art often result in products of reduced biological activity, when compared with those of the corresponding unbound biological material. These biological materials are known to be sensitive to thermal and chemical denaturation or inactivation. The loss of biological activity often results when immobilizing operations are carried out under harsh conditions which can be particularly problematic when polymer condensation reactions are involved. Furthermore, the products resulting from prior art methods are often disadvantageous with respect to their hydrophilicity, strength, durability, and porosity.
It therefore is an object of the present invention to develop a method of immobilizing biological materials that does not reduce the biological activity of the products.
It is a further object of this invention to develop a method of immobilizing biological materials wherein the resulting products exhibit excellent strength, durability, porosity, and biological stability. Yet another object of the invention is to provide a method of immobilizing a high quantity of biological material per unit volume of final support (high density).